The invention relates to a method of immobilizing biomaterial on a substrate with an Si.sub.3 N.sub.4 surface to which the biomaterial is covalently bonded by means of a bonding agent.
The immobilization of biomaterial is of substantial importance for the utilization of bioactivity particularly under liquid contact. It is very important in chemical processes as well as for an analysis in separating processes or for the recurrent utilization of the biofunction. Other areas of interest are in the pharmaceutical area, in medicine, and in environmental sciences.
Many attempts have been made to immobilize biomaterial on different surfaces, also mineral surfaces such as glass which generally is first silanized.
E. Tamiya et al, describe in the J. Mol. Cartal. 43(1988) 293-301, an immobilization of urease on a quartz crystal with a thin silver layer onto whose surface a silicon nitride layer is sputtered. The so treated crystal was stored in air for 24 hrs, was then washed and dried in air. Subsequently, .gamma.-aminopropyltriethoxysilane and then glutaraldehyde were vapor deposited on the surface. The so-generated thin organic surface film of about 100 A thickness is considered to have little porosity. A bonding of the silane and the aldehyde cannot clearly be observed.
The enzyme deposited on the film from an aqueous solution had an activity relative to the free urease of only 2.25%. This immobilization procedure does not appear to be fully satisfying.
It is the object of the present invention to provide a new type of biomaterial immobilization which requires only a small number of treatment steps and which provides relatively stable products in a reproducible manner.